I just joined this forum for some advice since we're new to the world of fancy mice. We did research before deciding to own them but now something has come up that's new to us. Grab a cup of tea! This could be a long post.

Background info: My 8 year old son is the owner of 2 male mice. Zisteau (tan/white) has always been slightly smaller and more social to humans. Etho (black/white) is a little larger and more timid around humans.They are littermates born from a friend's pets. Born in January 2014; we received them in early March 2014. They share a 10 gallon tank (with a lid) that includes 2 homes, 1 water bottle, 1 food bowl, 1 Silent Spinner wheel and various toys that we rotate out. Even though they have 2 homes, they often sleep together under one roof.

Etho has always seemed to be the dominant mouse, occasionally chasing Zisteau but not aggressively and never leaving visible injuries. Tuesday night, we noticed the tables turned and Zisteau was chasing Etho around but it did not seem harmful. Wednesday morning, we woke to find blood and small bite marks on Etho's tail. The spinning wheel had blood in it, too. I immediately separated them then transferred Zisteau to a borrowed cage. Etho's tail is healing and there's been no fresh blood in the tank since they separated. I did not treat his tail. I simply cleaned the tank, everything in it, and applied fresh bedding. As of this writing, they've been separated 24 hours. Both in their own spaces and in different rooms (We couldn't find a place in the home where we could put the tank and cage next to each other without our curious poodle causing them more stress.). Since the separation, they're both active in their own environments (eating, using wheel, etc). Zisteau seems more active than Etho. The bite marks on his tail are still visible but do not seem to bother him or look worse.

We knew from the start that male mice sometimes cannot live together but also read that they are social and same sex littermates often live together successfully. I would like to reintroduce for a short time today (30 minutes?) in our large bathtub (clean and drain is capped) to see how they interact. If all goes well, I would like to put them both back in the 10 gallon tank to see how they settle in again. Here comes my long list of questions:

1. Is it possible for them to live again in harmony in the same tank? If not, I can place a piece of plexiglass in the 10 gallon tank, essentially dividing it in two, but then they each have 1/2 the living space they did before, which is probably too small for one mouse.

2. Another suggestion was to get 2 permanent, separate living quarters but put them side by side so they can still see each other. That isn't my idea of being social but does that arrangement work for mice? Doesn't "social" mean more than looking at one another through glass? That would require purchasing another living space (roughly $50-60 US) AND having an area that could accommodate two separate living areas side by side...and we don't have anywhere in our home where we can do that. So--to be honest--even if that did work, that's not a viable option for us.

3. I've read that sometimes having 2 of everything is necessary for them to claim their own bit of territory within the living space. We currently have 2 homes. I can add a 2nd wheel, although it will take up space. Do we need 2 water bottles, too?

4. It was suggested to take out the food bowl and simply scatter the food throughout the tank so they can forage and not fight over ownership of the food bowl. How do we know when they need more food? Or do we just keep adding food every day, knowing some of it may go to waste?

5. If they have to be rehomed to a different family (which we would only do as a last resort), should we look for a family who will take them both but keep in separate but adjacent spaces?

6. Is there anything I'm not asking that I should be?

I appreciate any insight you can offer. I didn't expect owning mice to get complicated.

Update: They are both in the 10 gallon tank now with 2 water bottles, 2 homes (nesting areas...I'm still getting used to mouse-speak...smile), one Silent Spinner wheel and a cardboard tube. I've seen Zisteau approach Etho in (what seems to be) a non-agressive way or even pass by him, and Etho bolts like lightning. But there haven't been any squabbles yet. Is this a positive step in the right direction?

On another note, Zisteau has now taken to jumping from the top of his nesting home to the metal grate on top of the tank and walking upside down. This is new, probably because he was housed in a cage (metal bars) overnight and learned some new tricks. He definitely has more energy than Etho.

I received this advice from the breeder who gave me my dear boy mouse, Schtunkie, and then later from other mouse people. Although some people report strategies to keep two adult bucks from killing each other when they live together, in general it doesn't work. Two females will be fine as companions, but not males. I've heard repeatedly from mousekeepers who have tried to house two males together and ended up with at least one dead mouse. Baby males that were friends can suddenly change when they get older and kill each other. It is not uncommon for bucks to fight to the death. I guess they're very territorial. For that reason, Schtunkie has been a lone mouse. I have him as a pet, not for breeding. I give him a lot of handling and attention; he is very tame and curious. I used to vary his environment, but now that he is over two years old, he seems to prefer the same arrangement of stuff in his cage and the same toys.I hope you get some more feedback, but this has been my experience.jturner

Thanks for taking the time to respond to my post. They've been in side-by-side separate tanks since my original post and they both look healthy and no more behavior issues. Looks like we made it through to the other side.